Help me accessorise this dress for a wedding!

My brother is getting married in July and I have bought this Hobbs dress http://m.hobbs.co.uk/product-detail?productid=0113-5679-9028L00&productvarid=0113-5679-9028L00-WHITE CHINA BLU-10&refpage=hobbs-invitation/dresses&view=2&searchpage=1&pagesize=12 and matching blue suede slingbacks.

There was also a matching bag and a cocktail hat to go with it, but I thought too much china blue might look a bit matchy matchy, and anyway at £80 each I couldn't afford them!

So, any suggestions about a bag, jewellery, maybe a hat to go with it? All ideas gratefully received...